PHP fatal error : Call to a member function fetch() on boolean

Question

我试图编写一个登录脚本，需要用户先登录才能访问数据库，当我写出代码时，我在屏幕上登录，但屏幕显示此错误:PHP fatal error :在第 12 行调用 G:\xampp\htdocs\music\auth.php 中 bool 值的成员函数 fetch()

我不知道该怎么办。这是我的代码:

<?php
session_start();
$err = "";
if( !empty($_POST['submit']) )
{
    $name = $_POST['user'];
    $pwd = $_POST['password'];

    $music = new PDO('mysql:host=localhost;dbname=music', 'musicphp', 'password');
    $sql = "SELECT id FROM music WHERE username = '$name' AND pwd='$pwd'";
    $users= $music->query($sql);
    $music = $users->fetch();

    if( empty($users['id']) || $users == NULL )
    {
        $err = "Bad username or password";
    }
    else
    {
        $_SESSION['userid'] = $user['id'];
        header('Location: index.php');
    }
}
echo $err;
?>
<form action = "auth.php" method="post">
    Username: <input type="text" name="user"/>
    Password: <input type="password" name="password"/>
    <input type="submit" name="submit" value="Log in" />
</form>

Answer 1

请使用准备好的语句

去掉这部分

$sql = "SELECT id FROM music WHERE username = '$name' AND pwd='$pwd'";
$users= $music->query($sql);
$music = $users->fetch();

并以此替换它

$sql = "SELECT id FROM music WHERE username = :name AND pwd=:pwd";
$statement= $music->prepare($sql);
$statement->execute(array(':name'=> $name,':pwd'=>$pwd));
$music =  $statement->fetch();